Ground Water and the Evolution of Patterned Mires, Glacial Lake Agassiz Peatlands, Northern Minnesota

(1) The hydrogeological setting of the Glacial Lake Agassiz Peatlands in Minnesota was investigated by measuring ground-water levels in observation wells, by studies of soil types and thicknesses, and by computer model experiments to simulate ground-water flow. (2) Most ground water circulates along flow paths several kilometers long that pass through the peat column and into the underlying mineral soil. (3) Most ground-water flow is probably caused by the development and persistence of large raised bogs, and occurs because of ground-water mounds (elevated water tables) under the bogs. (4) Lateral bog growth may be limited by the neutralizing of bog water acidity by ground-water discharge ('artesian' flow) at raised bog margins.